The BUILT Strength Infinite Series Back Extension is a commercial-grade selectorized machine built to load the posterior chain directly and repeatedly — spinal erectors, glutes, and hamstrings working through a controlled extension arc with smooth, consistent resistance from a 200 lb weight stack. Pin-select adjustments keep load changes fast between sets, supporting everything from warm-up volume to heavy working sets.

Adjustable hip pads and handlebars let every user dial in the correct starting position — proper hip height and grip placement locked in before the first rep, keeping spinal alignment safe and the movement pattern repeatable across an entire session.

Primary muscles targeted

Secondary muscles

Key features

Specifications